An audio interface (such as a headphone socket) of an existing audio signal sending device (such as a mobile communication terminal) and an audio interface of an existing audio signal receiving device (such as a headphone) generally use a four-section interface, in which a pin 1 and a pin 2 are audio pins, i.e., a left-channel pin and a right-channel pin respectively. However, a pin 3 and a pin 4 of different types of audio interfaces play different roles, that is, there are two types of audio interfaces: the pin 3 is a MIC pin (a microphone pin) and the pin 4 is a GND pin (a ground pin); the pin 3 is a GND pin and the pin 4 is a MIC pin.
As different types of audio interfaces exist, if the audio interface of the audio signal sending device (such as the mobile communication terminal) and the audio interface of the audio signal receiving device (such as the headphone, a headset) do not match, the audio signal sending device can neither communicate with the audio signal receiving device via the MIC pin of the audio interface, nor transmit an audio signal to the audio signal receiving device via the audio pins (i.e., the left-channel pin and the right-channel pin) of the audio interface normally.
Therefore, whether for designing the audio signal receiving device (such as the headphone, a headset, a loudspeaker, an audio signal adapter device, and other audio signal receiving devices for receiving and processing the audio signal via the audio pins) which may be correctly adapted to the audio signal sending devices (such as the mobile communication terminal) with different types of audio interfaces, or for prompting a user whether the audio interface is matched with the audio signal receiving device with a voice or text prompting function, first of all, it is required to detect the type of the audio interface in the audio signal receiving device so as to detect the type of the audio interface of the audio signal sending device (such as the mobile communication terminal) currently connected with the audio signal receiving device.